How would I fix a executereader: connection property has not been initialized.'?

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1.00/5 (1 vote)

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I'm getting more into coding, I do apologize in advance. I am a novice myself.

C#

private void btnLogin_Click(object sender, EventArgs e)
{
    if (txtPassword.Text != string.Empty || txtUsername.Text != string.Empty)
    {
        SqlCommand cmd = new SqlCommand("select * from LoginTable where username='" + txtUsername.Text + "' and password='" + txtPassword.Text + "'", cn);
        SqlDataReader dr = cmd.ExecuteReader();
        if (dr.Read())
        {
            dr.Close();
            this.Hide();
            Form1 home = new Form1();
            home.ShowDialog();
        }
        else
        {
            dr.Close();
            MessageBox.Show("No Account avilable with this username and password ", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }

    }
    else
    {
        MessageBox.Show("Please enter value in all field.", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
    }
}

What I have tried:

I followed what was suggested from a previous error and generated a local for 'dr' however now I'm having issues with the Exception unhandled.
System.InvalidOperationException: 'ExecuteReader: Connection property has not been initialized.'
How would I initialize this property here?
SqlDataReader dr = cmd.ExecuteReader();

Posted 24-Nov-22 19:28pm

fallen caser

Updated 25-Nov-22 3:54am

PIEBALDconsult

v2

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RickZeeland · Answer 1 · 2022-11-24T19:52:00

You need a connection first, something like this:

using (SqlConnection cn = new SqlConnection()) {  
    cn.ConnectionString = "Server=[server_name];Database=[database_name];Trusted_Connection=true";  
    // using the code here...  
}

also see example here:
SQL Server Database Connection In C# Using ADO.NET[^]

And also: Retrieving Data Using a DataReader - ADO.NET | Microsoft Learn[^]

Your code is vulnerable to SQL injection, if you want to use your code in a production environment, use parameterized queries, see:
Using Parameterized Query to Avoid SQL Injection[^]

OriginalGriff · Answer 2 · 2022-11-24T19:55:00

So little code, so many errors ... most of which you haven't spotted yet ...

Lets start with the big one that you don't know about: Never concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Always use Parameterized queries instead.

When you concatenate strings, you cause problems because SQL receives commands like:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'Baker's Wood'

The quote the user added terminates the string as far as SQL is concerned and you get problems. But it could be worse. If I come along and type this instead: "x';DROP TABLE MyTable;--" Then SQL receives a very different command:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';DROP TABLE MyTable;--'

Which SQL sees as three separate commands:

SQL

SELECT * FROM MyTable WHERE StreetAddress = 'x';

A perfectly valid SELECT

SQL

DROP TABLE MyTable;

A perfectly valid "delete the table" command

SQL

--'

And everything else is a comment.
So it does: selects any matching rows, deletes the table from the DB, and ignores anything else.

So ALWAYS use parameterized queries! Or be prepared to restore your DB from backup frequently. You do take backups regularly, don't you?

And on a login screen? So I don't even have to sign up to destroy you stuff? :sigh:
Fix that through your whole app as a matter of urgency.

Second is one you haven't seen, put will ost you a lot of money, or possibly even time in jail. Never store passwords in clear text - it is a major security risk. There is some information on how to do it here: Password Storage: How to do it.[^]

And remember: if you have any European Union users then GDPR applies and that means you need to handle passwords as sensitive data and store them in a safe and secure manner. Text is neither of those and the fines can be .... um ... outstanding. In December 2018 a German company received a relatively low fine of €20,000 for just that.

When you have fixed that throughout your whole app, start thinking about the problem you have found. Which is trivial, if you read the error message. your SqlConnection cn has not been initialised - it's not an open connection to your database. So create the connection object, open it, use it for your code, and close and Dispose it.

How would I fix a executereader: connection property has not been initialized.'?

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